DE102016214997A1 - Method for operating a motor vehicle with a fuel cell system and with at least one energy storage device - Google Patents

Abstract

The technology disclosed herein relates to a method of operating a motor vehicle. The motor vehicle includes a fuel cell system and an energy storage device. The fuel cell system and the energy storage device are designed to provide electrical power for at least one drive motor. The method comprises the steps of: detecting an impending traffic jam; and adjusting the hybridization ratio of the energy storage device and the fuel cell system as a function of the impending traffic jam.

Description

The technology disclosed herein relates to a method of operating a motor vehicle having a fuel cell system and having at least one energy storage device.

Motor vehicles with a fuel cell system and with at least one energy storage device as such are known. The power of the fuel cell system can be calculated, for example, from the current driver request torque and the current vehicle electrical system load. In order not to burden the fuel cell system with power peaks from short-term accelerations, the power requirements of the fuel cell system can be filtered and the short power peaks taken from a high-voltage battery.

From the German patent application with the publication number DE 10 2014217780 A1 a method for the predictive operation of a fuel cell is known in which during a traffic congestion, a high-voltage storage provides the energy to drive the motor vehicle.

It is a preferred object of the technology disclosed herein to reduce or eliminate at least one disadvantage of the previously known solutions. It may be a preferred object of the technology disclosed herein to provide a method of operating a motor vehicle that has a good or better efficiency than previously known systems.

Other preferred objects may result from the beneficial effects of the technology disclosed herein. The object (s) is / are solved by the subject matter of claim 1. The dependent claims are preferred embodiments.

The technology disclosed herein relates to a method of operating a motor vehicle having a fuel cell system and to at least one energy storage device.

The technology disclosed here thus relates inter alia. a fuel cell system with at least one fuel cell. The fuel cell system is intended, for example, for mobile applications such as motor vehicles, in particular for providing the energy for at least one drive machine for locomotion of the motor vehicle. In its simplest form, a fuel cell is an electrochemical energy converter that converts fuel (e.g., hydrogen) and oxidants (e.g., air, oxygen, and peroxides) into reaction products, thereby producing electricity and heat.

An energy storage device is a device for storing electrical energy. For example, the energy storage device may be a high-voltage storage. Suitably, the energy storage device can be designed as a battery, in particular as a high-voltage battery. Alternatively or additionally, supercapacitors (in short supercaps or SC) may also serve as energy storage devices.

The energy storage device and the fuel cell system are designed to provide electrical power to at least one drive motor, preferably all electrical consumers of the motor vehicle.

The at least one electric drive motor may be an electric motor, which contributes to the propulsion of the motor vehicle. Preferably, the drive motor is an electric motor, which can regenerate electrical energy to the energy storage device by recuperation. Likewise, the motor vehicle disclosed herein may comprise a plurality of electric drive motors. The term "at least one drive motor" includes in the technology disclosed here embodiments with "a drive motor", with "several drive motors" and "with one or more drive motor (s) together with at least one or even all auxiliary consumers (n)" of motor vehicle. The auxiliary consumers may be ancillary consumers of the fuel cell system (e.g., oxidizer) or the motor vehicle (e.g., air conditioning).

The electric drive motor, the energy storage device and the fuel cell system are connected to each other via a corresponding power electronics. The energy storage device and the fuel cell system are in particular designed to supply the electric current to the electric drive motor via corresponding lines, which is necessary for driving the motor vehicle.

• – Erfassen eines bevorstehenden Verkehrsstaus.

The method disclosed herein comprises the step:

• - Detecting an impending traffic jam.

A traffic congestion in the sense of the technology disclosed here can also be referred to as a traffic jam and usually refers to a heavily stagnant or stalled traffic flow on a roadway. This means in particular that a number of vehicles per unit of time or per route length is greater than a predetermined threshold. In particular, there is a congestion when the traffic, so the vehicles, at a speed of less than 40 km / h, in particular less than 20 km / h, preferably less than 12 km / h flows. In such a traffic jam can the total power requirement of the motor vehicle for propulsion and for all secondary consumers are less than 20% or less than 10% or less than 5% of the rated power of the fuel cell system. A future or impending traffic jam is a traffic jam that already exists, but in which the motor vehicle is not yet located. An imminent traffic congestion in the sense of the technology disclosed here can in one embodiment also be predicted traffic congestion in front of a red traffic light, provided, for example, it is accompanied by a waiting time of more than 2 minutes or more than 2 minutes.

Methods are known in the art for detecting an impending traffic jam. For example, traffic jams can be detected using floating car data (FCD) or floating phone data (FPD) and / or stationary acquisition systems. The information about such a traffic jam can be transmitted to the motor vehicle via various communication paths and communication formats. For example, congestion information can be generated via the Traffic Message Channel (TMC) or other traffic telematics systems and transmitted to the motor vehicle. Likewise, a vehicle-to-vehicle communication is conceivable that informs about a traffic jam. Navigation devices already installed in motor vehicles today already use such methods for detecting a traffic congestion. However, other methods for detecting an impending traffic jam are also conceivable.

Preferably, the detection of a traffic congestion includes the detection of the exact position of the congestion and the extent of congestion. The extent of traffic congestion in the sense of the technology disclosed herein may include, but is not limited to: are characterized by the following quantities: length and / or duration of the congestion, average speed of traffic flow in congestion, number of vehicles per lane, etc. Preferably, the extent of the congestion is defined by the traffic jam length and the average speed of traffic flow in the traffic jam.

• – Anpassen von einem Hybridisierungsverhältnis von Energiespeichereinrichtung und Brennstoffzellensystem in Abhängigkeit von dem bevorstehenden Verkehrsstau vor dem Eintreffen am Verkehrsstau danach.

The method disclosed herein further comprises the step:

• Adjustment of a hybridization ratio of energy storage device and fuel cell system depending on the impending traffic jam before arriving at the traffic jam thereafter.

The hybridization ratio indicates how much power the at least one electric drive motor (preferably all electrical consumers of the motor vehicle) from the at least one energy storage device and how much power the at least one electric drive motor (preferably all electrical consumers of the motor vehicle) from the fuel cell system. Thus, the hybridization ratio also denotes the proportion of electrical power which the fuel cell system or the energy storage device respectively provide for the at least one electric drive motor, preferably for the total consumption of electrical energy of the motor vehicle

Pbat:

die dem mindestens einen elektrischen Antriebsmotor von der Energiespeichereinrichtung bereitgestellte Leistung; und

PFC:

die dem mindestens einen elektrischen Antriebsmotor von der Brennstoffzelle bereitgestellte Leistung ist.

The hybridization ratio H can be defined, for example, as H = Pbat / PFC (1), in which

Pbat:

the power provided to the at least one electric drive motor by the energy storage device; and

PFC:

which is the power provided to the at least one electric drive motor by the fuel cell.

However, other definitions are also conceivable.

The adaptation of the hybridization ratio may in particular comprise the steps according to which the electrical power supplied by the energy storage device to the at least one drive motor is increased prior to arrival at the traffic jam, and / or after which the traffic reduced by the fuel cell system reduces the electric power provided to the at least one drive motor becomes. For example, the electrical power provided by the fuel cell system can be reduced so that the fuel cell system provides no or only a small part of power for the electrical consumers of the motor vehicle. Preferably, the fuel cell system does not charge the energy storage device at this time. In other words, it may be provided at this time that the fuel cell system produces less than 100% of the electrical vehicle load and that electrical energy for the electrical consumers of the motor vehicle, in particular for the at least one drive motor, is taken from the at least one energy storage device.

• – Bestimmen von mindestens einem Parameter, der die vom mindestens einen Antriebsmotor, bevorzugt von allen elektrischen Verbrauchern, benötigte Energiemenge vom aktuellen Standpunkt des Kraftfahrzeugs bis zum bevorstehenden Verkehrsstau repräsentiert; und
• – Anpassen vom Hybridisierungsverhältnis vor dem Eintreffen am Verkehrsstau basierend auf den mindestens einen Parameter.

The technology disclosed herein may further include the steps of:

• Determining at least one parameter which determines the amount of energy required by the at least one drive motor, preferably by all electrical consumers, from the current standpoint the motor vehicle until the impending traffic jam represents; and
• Adjusting the hybridization ratio before arriving at the traffic congestion based on the at least one parameter.

The at least one parameter, which represents the amount of energy required, may be, for example, the distance and / or the time until the impending traffic jam. But there are also other parameters conceivable. Preferably, the method disclosed herein comprises the step of determining, based on the at least one parameter, the amount of energy needed to operate the motor vehicle until the impending traffic jam. The calculations to be carried out for this purpose are familiar to the person skilled in the art and, in addition to the aforementioned parameters, may also include further information, such as exact routing (e.g., uphill, downhill, etc.), the predicted consumption of the secondary consumers, the efficiencies of the various components, etc.

• – Bestimmen des Ausmaßes des Verkehrsstaus;
• – Anpassen vom Hybridisierungsverhältnis vor dem Eintreffen am Verkehrsstau in Abhängigkeit vom Ausmaß des Verkehrsstaus.

The technology disclosed herein may further include the steps of:

• - determining the extent of traffic congestion;
• - Adjusting the hybridization ratio before arriving at the traffic congestion depending on the extent of traffic congestion.

In particular, it is possible (preferably based on variables indicative of the extent of the traffic congestion) to determine the amount of electrical energy which will be provided by the fuel cell system in the traffic jam of the energy storage device and which is to be temporarily stored in the energy storage device during the traffic congestion. If the amount of energy that is to be supplied to the energy storage device during the traffic jam is known so that the fuel cell system can operate at an energy-efficient operating point, then the hybridization ratio can be set before the traffic jam arrives so that the energy storage device can absorb this amount of energy even in a traffic jam. For this purpose, additionally the current storage capacity of the energy storage device can be determined. The current storage capacity and the storage capacity required during the congestion result in a delta by which the energy storage device is to be unloaded until the traffic jam. The hybridization strategy can then increase the proportion of electrical power taken from the energy storage device such that the energy storage device also has the required storage capacity at the traffic jam. Preferably, therefore, the hybridization ratio before arriving at the traffic jam can be adjusted such that the amount of electrical energy provided by the fuel cell system in the traffic jam during the traffic jam in the energy storage device can be cached. However, it may also be the case that the current storage capacity is already sufficient for the charging process during the traffic congestion, then the hybridization ratio can remain unchanged.

• – Anpassen vom Hybridisierungsverhältnis vor dem Eintreffen am Verkehrsstau, wobei das Hybridisierungsverhältnis so angepasst wird, dass die Energiespeichereinrichtung vor dem Eintreffen am Verkehrsstau einen Ladungszustand aufweist, der unterhalb eines Staugrenzladungszustandes liegt.

The technology disclosed herein may further include the step of:

• Adjusting the hybridization ratio before arriving at the traffic jam, wherein the hybridization ratio is adjusted so that the energy storage device before arriving at the traffic jam has a charge state that is below a Staenkenzladungszustandes.

The Staugrenzladungszustand can be a state of charge (or SoC called) of the at least one energy storage device that can absorb enough energy from the fuel cell system in the congestion, so that the fuel cell system itself can be operated for the most part in an energy-efficient operating point. For example, the charge state SOCSTAU may be 5% or 10% or 20% or 30% of the maximum storage capacity.

The method disclosed herein may include the step of limiting the electric power (P _{BZ, j} ) produced by the fuel cell system to 1% to 40% of the rated power of the fuel cell system, preferably 3% to 20% of the rated power of the fuel cell system, and more preferably at 6% to 10% of the rated power of the fuel cell system. The fuel cell system is therefore preferably operated at an operating point or load point in which the fuel cell system can provide electrical power with a high degree of efficiency. Preferably, the electric power provided by the fuel cell system during the congestion is provided to the at least one drive motor. Typically, the fuel cell system produced more electrical power at such a high efficiency load point than the at least one prime mover needed during a traffic congestion. This additional electrical power can be stored in the energy storage device with the technology disclosed here. Thus, the overall efficiency of the motor vehicle can be improved as a rule.

The method disclosed herein may include the step of increasing the electrical power provided by the energy storage device prior to arriving at the traffic jam only when the state of charge of the Energy storage device is above a lower state of charge limit.

In other words, the technology disclosed herein relates to a method for efficiently operating a motor vehicle having a fuel cell system and having at least one energy storage device. During a journey the navigation device receives (for example by GPS) the information that a traffic jam is located about 10 km from the current position. In the traffic jam, the motor vehicle will be most of the time. According to the technology disclosed herein, the motor vehicle may be supplied with electric power in the traffic jam from the fuel cell system. Appropriately, the fuel cell system is operated at a load point, in which the fuel cell system has a high efficiency. As a rule, the fuel cell system produces more electrical power in this optimized load point than the motor vehicle (for example all drive motors and auxiliary consumers) needs in the traffic jam. The proportion of the electrical power that the motor vehicle does not need in a traffic jam can be temporarily stored in the energy storage device according to the technology disclosed here. For this purpose, the energy storage device is preconditioned before arriving at the traffic jam accordingly. A further advantage of the technology disclosed here is that the fuel cell system has comparatively high current densities in comparison to previously known solutions in the optimized load point, so that the fuel cell system can be operated at lower cell voltages. Thus, the degradation can be reduced

The technology disclosed here will now be explained by way of example with reference to the schematic figures. Show it:

1 a schematic diagram of the technology disclosed herein;

2 a schematic representation of the efficiency over the provided electrical power of the fuel cell system;

3 a schematic representation of a polarization curve of the fuel cell system; and

4 a schematic representation of the process steps of the method disclosed herein.

In the 1 At time t ₀ , the vehicle recognizes that a traffic jam begins at a distance E ₀ . This information can be provided for example by the integrated in the motor vehicle navigation device. Until arriving at the traffic jam at time t ₂ , the motor vehicle can continue to be operated at a normal speed, for example 100 km / h. For this normal speed operation, for example, the motor vehicle may require an electric power P _{KFZ, n} of 50 kW. If no traffic jam had been detected, this 50 kW electric power would be provided entirely by the fuel cell system. Only for short peak loads, for example in the period t ₁ , would the energy storage device, for example a high-voltage storage battery, provide additional electrical energy.

According to the technology disclosed here, the hybridization ratio is now changed by the fuel cell system instead of 50 KW provides only the electrical power P _{BZ, n,} for example, 40 kW (see dash-dotted line in 1 ). The missing electrical power P _{HV, n} (here 10 kW) is now released from the high-voltage storage battery to the motor vehicle (see dotted line in 1 ). The dashed line shows the state of charge SOC of the high-voltage storage battery. Since electrical power P _{HV, n is} continuously removed from the high-voltage storage battery while the vehicle is driving until the traffic jam _, the high-voltage storage battery discharges successively until time t ₂ . Any Peaklasten, such as in the period t ₁ , can continue to be additionally removed from the high-voltage storage battery. At time t ₂ , the high-voltage storage battery then has a comparatively low SOC.

In the traffic jam itself, the motor vehicle, including all drive motors and auxiliary consumers, requires an electrical power P _{KFZ, j} , which is generally much lower than the electrical power P _{KFZ, n} , which is required during normal operation. For example, this electrical power consumption P _{KFZ, j can} be many times lower than the electrical power consumption P _{KFZ, n} during normal operation. The amount of electrical energy that is taken from the high-voltage storage battery before arriving at the traffic jam can be so dimensioned that the high-voltage storage battery can store the proportion of electrical power P _{BZ, j} provided by the fuel cell system in the energy-efficient load point during congestion is not needed instantaneously by the motor vehicle. Alternatively, it may be provided that such a prognosis of the power consumption in the traffic jam is dispensed with and that at the beginning of the traffic jam at the time t ₂ a charge state of the high-voltage storage battery should be reached.

In the traffic jam, therefore, the electrical power required by the motor vehicle is completely provided by the fuel cell system. The fuel cell system is advantageous in an energy-efficient load point (see. 2 ) operated. The fuel cell system then produces in this load point requires more electrical power than the motor vehicle. The excess portion is stored in the high-voltage storage battery. Accordingly, the SOC curve for the state of charge of the energy storage device slowly rises again during the congestion. After the traffic jam, the motor vehicle can be operated again in normal operation. Here, for example, it may be provided that the fuel cell system again provides the entire electrical power P _{KFZ, n '} for the motor vehicle.

The 2 schematically shows the efficiency of the fuel cell system for various electrical services. The efficiency of the fuel cell system in normal operation (eg at 50 kW) is significantly lower than in the area P _{BZ, j} , in which the fuel cell system is operated during the traffic congestion. It will be readily apparent that the overall efficiency of the motor vehicle is improved by the technology disclosed herein.

Could the motor vehicle cached no electrical energy during the traffic jam in the high-voltage storage battery, so the fuel cell system would have to be operated in a load point in which even lower electrical power than P _{BZ, j} , are delivered. The 3 schematically shows the polarization curve of the fuel cell system disclosed herein. It can be seen from the polarization curve that at electrical output powers below P _{BZ, j} , (here the corresponding current density to P _{BZ, j} , is entered) very small current densities occur, which are accompanied by very high cell voltages. These high cell voltages lead to a comparatively high cell degradation.

The 4 schematically shows a flowchart of the method disclosed here. The process starts with step S100. First, in step S200, a subroutine that can detect a traffic jam is traversed here. For this purpose, a wide variety of technologies can be used, which are familiar to the expert. In step S300 it can be checked whether there is a traffic jam. If there is no traffic jam, the distance to the traffic jam can be determined in step S400. On the basis of the distance to the traffic jam and other operating parameters of the motor vehicle, in particular the fuel cell system and / or the energy storage device, the required amount of energy can be determined, which requires the motor vehicle to get to the traffic jam (see step S500).

• – die von dem im energieeffizienten Lastpunkt betriebenen Brennstoffzellensystem während des Verkehrsstaus bereitgestellt wird,
• – die von dem mindestens einen Antriebsmotor (bevorzugt von allen elektrischen Verbrauchern des Kraftfahrzeugs) während des Verkehrsstaus instantan nicht benötigt wird, und
• – die während des Verkehrsstaus in der Energiespeichereinrichtung gespeichert werden soll.

In step S610 it can be provided that the energy quantity is determined at time t ₀ ,

• - provided by the fuel cell system operated in the energy-efficient load point during the congestion,
• - which is instantaneously not needed by the at least one drive motor (preferably of all electrical consumers of the motor vehicle) during the traffic congestion, and
• - which is to be stored in the energy storage device during traffic congestion.

Alternatively or in addition, that the amount of energy is determined at the time t _0, which is to be taken from the high-voltage storage battery, a storage limit state of charge at the time t to reach ₂ may be provided in step S620.

In step S700, it may be provided that the hybridization ratio of the fuel cell system and at least one energy storage device is adapted. As a rule, the hybridization ratio is adjusted here so that more energy is taken from the high-voltage storage battery for instantaneous supply of the electrical load of the motor vehicle and at the same time less electrical energy is provided by the fuel cell system for instantaneous supply of electrical consumers of the motor vehicle.

But that does not have to be this way. If, at time t _0, the high-voltage storage battery is already discharged to such an extent that the excess electrical power provided by the fuel cell system in the energy-efficient load point during the congestion can be stored in the high-voltage storage battery, the fuel cell system can continue to be operated at the normal load point.

In step S800 it is checked whether the motor vehicle is already in traffic jam. If this is not the case, then it can be provided that the preceding steps are repeated. In other words, therefore, the adaptation of the hybridization ratio disclosed here on the basis of instantaneous traffic data can be continually checked and optionally retuned.

If it is determined in step S800 that the motor vehicle is in a traffic jam, the fuel cell system is operated in a load point with energy-efficient power output in step S900 (see FIG. 3 ).

The foregoing description of the present invention is for illustrative purposes only, and not for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102014217780 A1 [0003]

Claims (8)

 A method of operating a motor vehicle having a fuel cell system and at least one energy storage device, wherein the fuel cell system and the energy storage device are configured to provide electrical power to at least one electric drive motor, comprising the steps: - detecting an impending traffic jam; and - Adjusting the hybridization ratio of energy storage device and fuel cell system depending on the impending traffic jam. The method of claim 1, wherein adjusting the hybridization ratio comprises the steps of increasing the electrical power (P _{HV, n} ) provided by the energy storage device to the at least one drive motor, and then reducing the electrical power (P _{BZ, n} ) provided by the fuel cell system becomes.  Method according to one of the preceding claims, further comprising the steps: Determining at least one parameter representing the amount of energy required by the at least one drive motor until the traffic congestion occurs; Adjusting the hybridization ratio based on the at least one parameter.  Method according to one of the preceding claims, further comprising the steps: - determining the extent of traffic congestion; Adjusting the hybridization ratio depending on the extent of the congestion.  Method according to one of the preceding claims, further comprising the steps: Determining the amount of electrical energy to be provided by the fuel cell system in the traffic jam that is to be temporarily stored in the energy storage device during the traffic congestion; and - Adjusting the hybridization ratio, wherein the hybridization ratio is adjusted so that the provided by the fuel cell system in the traffic jam amount of electrical energy can be cached in the energy storage device.  Method according to one of the preceding claims, further comprising the step: - Adjusting the hybridization ratio, wherein the hybridization ratio is adjusted so that the energy storage device has a state of charge, which is below a Staenzenzladungszustandes. Method according to one of the preceding claims, wherein the provided by the fuel cell system in the traffic jam electric power (P _{BZ, j} ) is limited to 1% to 40% of the rated power of the fuel cell system, preferably to 3% to 20% of the rated power of the fuel cell system, and more preferably to 6% to 10% of the rated power of the fuel cell system.  Method according to one of the preceding claims, wherein the provided by the energy storage device before the arrival of the traffic jam electrical power is only increased when the state of charge of the energy storage device is above a lower state of charge limit.

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